Melanoma

Melanoma is a malignant tumour of melanocytes. Melanocytes predominantly
occur in the skin but can be found elsewhere, especially the eye. The vast
majority of melanomas originate from the skin.

Causation

Solar radiation is the major causative factor and the risk is related to:

   * The degree of solar exposure.
   * The age at which solar exposure occurs
   * Natural skin pigmentation.

Exposure during childhood is a more important risk factor than exposure in
adulthood. (This is seen in migration studies in Australia where people tend
to retain the risk profile of their country of birth if they migrate to
Australia as an adult). Fair and red-headed people are at greater risk.

Other risk factors include the "Dysplastic naevus syndrome" which is a
familial condition of atypical moles carrying a low to moderate risk of
acquiring melanoma.

Behaviour

Features that affect prognosis are tumor thickness in mm (Breslow depth),
depth related to skin structures (Clarke), type of melanoma, presence of
ulceration, presence of satellite lesions, and presence of regional or
distant metastasis.

With regard to tumor thickness at the time of diagnosis: thin melanomas
(<0.75mm) have a good prognosis, i.e. they can usually be cured by surgical
excision alone; tumors of more than 4 mm thickness at the time of diagnosis
are very often metastatic and can show very aggressive growth.

Types of melanoma

   * Superficial spreading (often fairly thin).
   * Nodular (often deeper)
   * Acral lentiginous (on soles and palms).
   * Hutchinsons melanotic freckle (often in older patients).

Symptoms

Diagnosis of melanoma requires expert knowledge, as early stages may look
identical to harmless moles. Signs and symtoms of melanoma include:

   * darkly pigmented skin lesion, sometimes with areas of little
     pigmentation
   * irregularly shaped skin lesion
   * growth or change in shape
   * itching, ulceration or bleeding

Treatment

Surgical excison - usually curative in thin lesions. Immunotherapy and to a lesser 
extent chemotherapy may have a somewhat experimental role in advanced tumours.

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